Do a little snorkeling in Mexico, and you'll soon be wracked with envy whenever you have to share a boat with a pack of scuba divers. I came down with this affliction several years ago on Baja's East Cape and got so far as to complete the course work, but I was grounded by a hurricane that brushed the coast before I ever hoisted a tank. Since then, my travels have taken me most often to the Yucatán Peninsula, where the warm Caribbean's aqua, teal and indigo striations and hallucinatory clarity have piqued memory of that lost opportunity into a gentle obsession.

Mexico's Caribbean coast is as close to ideal for a scuba beginner as you can get. It flanks the Great Maya Reef chain, second-largest in the world after Australia's Great Barrier Reef. Capable dive instructors are as plentiful as iguanas, and when you break from the intricacies of nitrogen intake and pressure gauges, you have Maya ruins and friendly villages to explore, comfortable hotels and great restaurants at your disposal, and as much nightlife as you can handle. It may not be so for the skilled and slightly world-weary divers whose next stop is Thailand, Mauritius or the Red Sea, but for a beginner the right patch of terra firma is just as important as what's underwater. Open-water certification courses take four days, more of it on land than in the water.

Here are my best scuba spot candidates so far. Cancún dropped off the list early on; though its shallow reef and colorful marine life are certainly suited to beginners, the underwater scenery can't compare to nearby spots, and there are other places where I'd rather spend my time. Tulum was another early casualty, with a stunning reef just beyond its world-famous beaches, but dive operators who concentrate almost exclusively on cenote and cave diving, which is not for beginners.

Cozumel — Widely considered Mexico's top diving destination and one of the best in the world, with a multitude of reefs and a marvelous variety of caves, caverns and tunnels to explore.

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Pros: Dozens of dive operators and even more dive sites; a laid-back, small-town atmosphere once you get away from the port.

Cons: Heavy cruise-ship and ferry traffic bringing swarms of mostly North American tourists; many dive shops right in the thick of the hubbub; huge popularity with divers creates more intimidating situations for beginners.

Playa del Carmen — No longer the humble fishing village that once made it a secret escape, but its stretch of reef almost rivals Cozumel's.

Pros: Abundance of sites with gentle currents; wealth of reasonably priced dive shops; some of the coast's best cenote diving; combo diving/Spanish courses available; plenty of comforts and activities.

Cons: Busy, commercialized and sometimes crowded, though with a more European, cosmopolitan air; ever more luxurious resorts popping up like pimples on a preteen; high food and lodging prices.

Isla Mujeres — Beyond the gleaming white sand beaches that give the "Island of Women" a reputation for seducing visitors into staying long past their intended departure date, turquoise waters harbor varied and vibrant sea life.

Pros: Nearly imperceptible currents on protected west shore ideal for beginners; reasonable prices at a handful of well-regarded dive shops; town has languid, tropical air and is a bargain for the region.

Cons: Truly varied terrain, including a couple of shipwrecks, on the rougher Caribbean side, is best for advanced divers; during peak season, town can get swamped by day-trippers from ferries and party boats.

Puerto Morelos — Small, colorful fishing village whose idyllic atmosphere recalls the Playa del Carmen of old, with the reef running closer to shore than anywhere on the coast.

Pros: National Marine Park keeps reef in pristine condition; competent and responsible dive shops; genuinely friendly and relaxed town; less expensive than most of Riviera Maya.

Cons: Beaches fill with seaweed and turtle grass; many places close during low season; boat traffic between reef and shore preclude swimming to the reef despite its proximity.

Akumal — Coral is less dramatic than at other Riviera Maya spots but brims with colorful sea life and has cachet as the birthplace of scuba diving on Mexico's Caribbean.

Pros: Reef diving easy and fun in protected bays; abundance of cenotes makes it one of the top cavern diving spots; top sea turtle-nesting site on town beach; laid-back, eco-conscious settlement with little commercialism.

Cons: Only a couple of hotels among a plethora of vacation rental properties; few bargains in upscale resort area that was Riviera Maya's first.

Costa Maya — Just beginning to be discovered, the southernmost coast consists primarily of two towns, Mahahual of cruise port fame and Xcalac to the south — plus the Chinchorro Bank, one of the Caribbean's largest and least-visited coral atolls.

Pros: Terrific diving in marine reserve known for wondrous coral formations, gigantic sponges and teeming sea life; little chance of crowding on long stretch of barely developed coastline.

Cons: Relatively few dive operations; Mahahual gets pretty trashy on cruise ship days but the reef is just offshore; Xcalac has stellar diving in its own national reef park, but Chinchorro is a 1½ or 2-hour boat ride away.

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